Crystal Structure of (NbSe4)3I and (NbSe4)10/3I CDW Compounds at 14 K

Abstract

Both (NbSe4)3I and (NbSe4)10=3I compounds are interesting system possessing quasi one-dimensional linear chain character and exhibiting nonlinear transport properties with a second order phase transition. The compounds are built of NbSe4 antiprisms, stacked along the tetragonal c axis into chains in a screw-like arrangement. Performed X-ray low temperature single crystal diffraction measurements allowed to solve, refine and analyze crystal structures of both compounds at 14 K. While (NbSe4)10=3I compound undergoes structural phase transition to monoclinic phase, (NbSe4)3I remains in tetragonal symmetry. Iodine atoms are responsible for the differences in (NbSe4)10=3I and (NbSe4)3I structures causing different spacing in the infinite NbSe4 chains.